Rigid disk drive with dynamic head loading apparatus

ABSTRACT

In one embodiment, a rigid disk drive including a rotary actuator having a lift tab extending asymmetrically from the end of the load beam which supports a slider with read/write element is disclosed. The free end of the lift tab cooperates with a cam surface on a cam assembly to provide dynamic loading and unloading of the slider while imparting a roll to the slider as it is loaded to and unloaded from the disk. In another embodiment, the lift tab extends from the end of the load beam along an axis generally parallel to the longitudinal axis of the load beam, but the axis of the lift tab is offset from the longitudinal axis of the load beam. In a further embodiment, a disk drive including a rotary actuator having a load beam which includes a lift tab extending from the free end, with the lift tab cooperating with a cam assembly which is located adjacent to the edge of recording media, but not extending over a surface of the media is provided.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent applicationSer. No. 07/766,479, filed Sep. 25, 1991 by James H. Morehouse, David M.Furay, James A. Dunckley and Bruce D. Emo, entitled "Rigid Disk DriveWith Dynamic Head Loading Apparatus", now U.S. Pat. No. 5,237,472,issued Aug. 17, 1993 which was a continuation-in-part of U.S. patentapplication Ser. No. 07/629,957 filed Dec. 19, 1990 by James H.Morehouse, David M. Furay and James A. Dunckley, entitled "Rigid DiskDrive With Dynamic Head Loading Apparatus" now U.S. Pat. No. 5,289,325,issued Feb. 22, 1994.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to the field of information storage utilizingrigid disks, and more particularly to apparatus for dynamically loadingand unloading read/write magnetic recording elements for flight abovethe surface of moving magnetic media.

2. Description of the Prior Art

In certain types of disk files which include rigid magnetic media it isdesirable to load and unload a magnetic recording reproducing elementinto flight above the surface of the moving media as opposed toutilizing take off from and landing on the magnetic media where themagnetic recording element comes to rest on the disk after rotation hasceased and takes off from the disk after the disk is once again spun up.U.S. Pat. No. 4,535,374 to Anderson et al., issued Aug. 13, 1985, isexemplary of a rigid disk drive of the linear actuator type whichprovides for dynamic loading of magnetic read/write heads above thesurface of a disk. In Anderson et al. a stationary cam follower isprovided on and supported from the housing, and the load arm, whichincludes a magnetic recording head at its free end, is provided with acam surface intermediate the free end and the end supported by theactuator. The cam surface cooperates with a stationary cam to lift thehead above the surface of the disk when the head arm is retracted.

Another linear actuator rigid disk drive utilizing a cam arrangement toachieve dynamic loading of the magnetic recording head above the disk isillustrated in U.S. Pat. No. 4,663,682 to McNeil, issued May 5, 1987. InMcNeil, a pair of cam surfaces are supported by the disk drive housingand a wing, having a pair of free ends, is attached to the load beamintermediate the actuator driving mechanism and the free end of the loadbeam which supports the head slider. The free ends of the wing cooperatewith the cam surfaces to lift the magnetic recording head slider abovethe surface of the disk when the head arm is retracted. In McNeil, thedirection of movement of the magnetic media beneath the magneticrecording head is such that the media is moving in a direction which isparallel to the longitudinal axis of the slider on which the magneticrecording element is supported and perpendicular to the longitudinalaxis of load beam. The cam surfaces in McNeil are offset and providepitch to the slider during the loading process when the slider isapproaching the surface of the rotating media.

U.S. Pat. No. 4,933,785 to Morehouse et al., issued Jun. 12, 1990, andassigned to Prairietek Corporation, discloses a magnetic disk driveutilizing a rotary actuator. The load beams (which support theread/write elements) each include a lift button which is supported onthe load beam, and positioned on the longitudinal axis of the load beam.The lift buttons cooperate with a spreader, which includes cam surfaces,to provide dynamic loading and unloading of the slider which issupported on the end of the load beam opposite of the pivot point of theload beam. The buttons and the cooperating spreader with cam surfacesare located intermediate the pivot point of the rotary actuator and themagnetic head. The button and cam surface on the spreader provide asymmetrical lift to the load beam and correspondingly symmetricalloading of the magnet head above the media, which in this configurationis rotating in the direction beneath the head which is substantiallyparallel to the longitudinal axis of the load beam which is supportingthe slider.

A later introduced rigid disk drive from Prairietek Corporation,utilized a dynamic loading structure having a cam surface supported onthe housing which contacted directly the load beam of the rotary armhaving the magnetic slider on its free end. In this Prairietek hard diskdrive, denominated the model 120, the cam is supported on the housingand is positioned intermediate the head slider and the pivot point ofthe rotary actuator. The principle distinction between the dynamicloading structure in the model 120 over the structure illustrated in the'785 patent is the elimination of the button which was included on theload beam and provided a center line lift on the load beam. In the model120 disk drive a heavy roll torque is applied to the load beam and thereis no ability to change the amount of torque and correspondingly theroll applied to load beam.

U.S. Pat. No. 3,984,873, issued Oct. 5, 1976 to Pejcha illustrates astructure for dynamically loading heads, which in one embodimentutilizes a movable channel member which is supported above the surfaceof the rotating rigid disk. The loading of a head above the surface ofthe disk is achieved by providing flat spring extensions which extendsymmetrically from the free end of the load beam and are captured in thechannel which is positioned in a plane above the surface of the disksuch that the opening is generally parallel to the plane of the disk.With the spring extensions captured in the channel, the heads areprevented from being loaded on the disk. To load the heads the channelmember is moved out of contact with the flat spring extensions and theheads move toward the surface of the associated disk. In anotherembodiment, the flat spring extensions on the ends of the load beam arecrisscrossed and a pivoted member is moved into contact with thecrisscrossed free ends to unload the heads from the disk. In a thirdembodiment, a cam surface is provided adjacent to the edge of therotating disk and the magnetic head is supported on a spring memberwhich is affixed by bolts to a rotating arm. An extension of the springmember on the end adjacent to the magnetic head is positioned at rightangles with respect to the center line of the rotary arm on which thehead and spring is mounted, with the spring extension having alongitudinal axis which is parallel to the longitudinal axis of the camsurface.

U.S. Pat. No. 5,027,241, issued Jun. 25, 1991 to Hatch et al.illustrates a rotary actuator using a dynamic loading tab which extendsfrom the end of the load beam. In Hatch et al., the load tab (whichcooperates with a cam for loading and unloading the slider from thesurface of the disk) extends outwardly from the end of the load beam andis symmetrically aligned with the centerline of the load beam. Althoughthis provides geometric symmetry, it does not provide zero torque on theload beam as it is lifted from the disk. In contrast, in accordance withone embodiment of the present invention an asymmetrically positionedlift tab is used whereby the amount of roll provided to the slider as itis lifted from the surface of the disk can be fine tuned to an optimumlevel. In a second embodiment of the present invention a lift tabstructure which provides a zero torque force on the load beam isprovided. This is achieved by utilizing an offset load tab.

A number of the prior disk drives employing dynamic head loadingutilized a cam arrangement in which a portion of the cam extended overthe surface of the magnetic recording disk. With the continuing desireto produce disk drives which are more compact, the requirement of havinga portion of the cam surface extend above the surface of the disk madeit more difficult to reduce the disk-to-disk spacing, and accordinglymore difficult to reduce the height of the disk drive. Additionally,this requirement made it more difficult to design an effective cam inview of constraints, such as, the type of material from which the camcould be constructed. This is particularly troublesome in drives using aplurality of disks where all of the disk surfaces are used for storinginformation. Additionally, in disk drives in which a portion of the camsurface extended above the magnetic disk, assembly of the drive was madesomewhat more difficult since if the cam assembly were installed priorto installation of the magnetic disks in the housing, it was necessaryto either pivot the cam assembly out of the way of the disks duringinstallation or to install the cam assembly after the disks had beeninstalled. In accordance with one embodiment of the present invention, acam assembly is provided which is constructed such that no portion ofthe cam assembly extends over a surface of any of the recording disks,thus eliminating the necessity to take special precautions wheninstalling the magnetic disks, and secondly eliminating the necessity ofproviding space for portions of the cam surfaces between adjacent disks.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a rigid disk drivewhich includes a dynamic head loading structure which imparts a roll tothe head slider as it is being loaded onto a rotating disk. Anotherobject of the present invention is to provide means to control thedynamic head loading structure such that the amount of roll imparted tothe head slider is adjustable. An additional object of the presentinvention is to provide a dynamic head loading structure which provideszero torque on the load beam as it is being lifted from the surface ofthe disk. A further object of the present invention is to provide adynamic head loading structure for a rotary actuator in which the rotaryactuator can be loaded into operative relationship with a cam assemblyfrom the back side of the cam assembly to simplify the initial assemblyof the rotary actuator structure in the drive as well as avoidingdamaging the disk surface. A further object of the present invention isto provide a dynamic loading structure which is uncomplicated and can beconstructed from readily available components. A further object of thepresent invention is to provide a means to protect the magnetic heads ofa rigid disk drive which are facing when the heads are unloaded from thesurface of the disk. Yet another object of the present invention is toprovide a disk drive with dynamic head loading structure which utilizesa cam assembly which does not extend within the area of the magneticrecording disks.

In accordance with one embodiment of the present invention, a lift tabis provided on the free end of an actuator arm which supports a sliderfor travel on an air bearing above the surface of a rigid magneticrecording disk. The lift tab is positioned such that is extends from thefree end of the actuator arm at an angle which is skewed from thelongitudinal axis of the actuator arm. The lift tab cooperates with acam surface (which is supported on the baseplate) and as a result of theasymmetrical location of the lift tab with respect to the longitudinalaxis of the actuator arm, the actuator arm is pivoted, which provides aroll orientation to the slider as it is loaded onto the disk.

In accordance with a second embodiment of the present invention, thelift tab provided on the free end of the actuator arm is positioned inan axis which is displaced from the longitudinal axis of the load beamby an amount which is selected such that the lifting force on the loadbeam is applied generally along the longitudinal axis of the load beamto avoid any twisting torque being applied to the load beam.

In accordance with a third embodiment of the present invention, adynamic load beam structure is provided in which the lift tab having theoffset end portion is a separate structural element from the main bodyof the load beam.

In accordance with a fourth embodiment of the present invention, a diskdrive is provided which features a dynamic head loading structure inwhich a cam assembly is positioned adjacent to the edge of a rotatingmagnetic disk and in cooperation with a head gimbal assembly having alift tab extending beyond the magnetic transducer utilized on the headgimbal assembly provides dynamic head loading without the necessity ofhaving any portion of the cam assembly positioned within the areabounded by the magnetic recording disk.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects and advantages of the invention will become apparent froma study of the specification and drawings in which:

FIG. 1 is a top plan view of a rigid disk drive incorporating thedynamic head loading apparatus in accordance with the present invention;

FIG. 2 is a top plan view of the down-facing head gimbal assemblyutilized in the rigid disk drive of FIG. 1;

FIG. 3 is a perspective view of the head gimbal assembly of FIG. 2;

FIG. 4 is a perspective view of the lower side of the head gimbalassembly illustrated in FIG. 3;

FIGS. 5a-5c illustrate the structure for achieving negative roll, noroll and positive roll for a slider supported on a head gimbal assembly;

FIGS. 6 to 8 illustrate, respectively, a slider having a negative roll,no roll and positive roll attitudes;

FIG. 9 is a highly enlarged view of a portion of the disk driveillustrated in FIG. 1 showing the head gimbal assembly in a plurality oflocations in its travel with respect to the cooperating cam assembly;

FIG. 10 is a cross-sectional view taken along the lines 10--10 in FIG.9;

FIG. 11 is a cross-sectional view taken along the line 11--11 of FIG. 1;

FIG. 12a is a plan view of a load beam utilized in the second dynamichead-loading embodiment of the present invention;

FIG. 12b is a view taken along lines 12b--12b in FIG. 12a;

FIG. 12c is a view taken along lines 12c--12c in FIG. 12a;

FIG. 12c-1 is a top plan view of a portion of a load beam used in thesecond embodiment of the present invention;

FIG. 12c-2 is a cross sectional view taken along lines 12c-2--12c-2 inFIG. 12c-1;

FIG. 12d is a cross-sectional view taken along lines 12d--12d in FIG.12a;

FIG. 12e is a cross-sectional view taken along lines 12e--12e in FIG.12a;

FIG. 12f is a cross-sectional view taken along lines 12f--12f in FIG.12a;

FIG. 12g is a top-plan view of a load beam used in the dynamic head-loadversion of drive in accordance with the present invention;

FIG. 12h is a view taken along lines 12h--12h in FIG. 12g showing theload beam in the loaded position;

FIG. 12i illustrates the load beam in FIG. 12h, but in an unloadedposition;

FIG. 12j is a perspective view of flexure 184;

FIG. 13 illustrates is plan view a third embodiment of the presentinvention;

FIG. 14 illustrates in an exploded form major elements of the dynamicload beam in accordance with the third embodiment of the presentinvention;

FIG. 15 is a top plan view of a disk drive in accordance with a fourthembodiment of the present invention;

FIG. 16 is another top plan view described in accordance with the fourthembodiment of the present invention;

FIG. 17 is a top plan view of a down head gimbal assembly utilized inthe present invention;

FIG. 17A is a view taken along the lines 17A--17A of FIG. 17;

FIG. 18 is a top plan view of a cam assembly utilized in the fourthembodiment of the present invention;

FIG. 19 is a view taken along the lines 19--19 of FIG. 18;

FIG. 20 is a view taken along the lines 20--20 of FIG. 18;

FIG. 21 is a view taken along the lines 21--21 showing the upper camassembly and portion of the recording disk 152;

FIG. 22 is a view taken along the lines 22--22 of FIG. 21; and

FIG. 23 is a view taken along the lines 21--21 of FIG. 16 showing thetwo disks utilized in disk drive 151 as well as upper and lower camassemblies 161 in a stacked configuration.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1, rigid disk drive 1 in accordance with the firstembodiment present invention illustrated in a top plan view. Rigid diskdrive 1 is illustrated in highly enlarged scale for illustrativepurposes. Included in rigid disk drive 1 is rigid disk 2, which mayinclude magnetic coated surfaces for the recording and reproduction ofdigital information. Rigid disk 2 is supported for rotation by asuitable motor and spindle combination (not shown). Clamp 4 securesrigid disk 2 to hub 5 of the motor for rotation with the rotor portionof the motor. Rigid disk drive 1 utilizes a rotary actuator whichincludes actuator body 6 which rotates about a center of rotation 7. Asuitable coil and permanent magnet motor (not shown) of the type wellknown in the art are positioned beneath return plate 8 of the permanentmagnet actuator motor assembly. Although in the disclosed embodiment ofthe invention a permanent magnet motor is used to position the actuator,other types of suitable drive mechanisms may be used for moving therotary actuator. Head gimbal assembly 9 is secured to actuator body 6and rotates about center of rotation 7. Head gimbal assembly 9 includesa generally flat, triangular shaped load beam 10 which supports near itsfree end a slider body 11 which includes a read/write element forwriting information to and reading information from magnetic recordingdisk 2. Attention is directed to FIGS. 2, 3 and 4 where additional viewsof head gimbal assembly 9 are illustrated. In accordance with thepresent invention, a second head gimbal assembly may be utilized beneaththe surface of rigid disk 2 to provide for record and reproduction ofdata on the lower surface of rigid disk 2. Head gimbal assembly 9includes lift tab 12, which in the embodiment illustrated comprises arod, which is suitably affixed to the upper surface of load beam 10.Alternatively, the lift tab could be formed integrally with the loadbeam. Although in the embodiment illustrated herein lift tab 12 ispositioned on the side of load beam 10 which is beyond (with respect tothe center of disk 2) center line 18, lift tab 12 could be positioned onthe other side of center line 18 (that is between center line 18 and theedge of load beam 10 which is nearer the center of disk 2). Supported inoperative relationship with the free end 13 of lift tab 12 is a camassembly 14 which is supported on baseplate 3. Included on cam assembly14 is cam surface 15, the contour of which will be best appreciated byreference to FIG. 6. Load beam 10 of head gimbal assembly 9 provides adownward force (when viewed as illustrated in FIG. 1) which maintainsfree end 13 of lift tab 12 in contact with cam surface 15. As will beappreciated by reference to FIGS. 1, 5 and 6, a portion of cam surface15 extends over the upper surface of rigid disk 2. Cam assembly 14 isaffixed to baseplate 3 using a suitable fastening means, such as a bolt16 having a threaded end (not shown) which cooperates with a threadedopening (not shown) in baseplate 3. As illustrated in FIGS. 1 and 5,cross-shaped slot 17 permits adjustment of cam assembly 14 in thedirections indicated by the arrows in FIG. 5. Adjustability of camassembly 14 in the direction of arrows which are generally radial withrespect to the disk provides the ability to vary the landing position ofthe slider on the disk and thereby compensate for manufacturingtolerances. Load beam 10 may be constructed of 0.0025" thick, 300 seriesstainless steel, although other material may be utilized. In theembodiment illustrated herein, lift tab 12 comprises a stainless steelrod and Delrin (an acetal resin compound) is used for cam surface 15.This combination of materials provides a low friction interface, howeverit will of course be appreciated that other combinations of materialsmay be utilized. Other suitable low friction materials, such as anacetal resin compound impregnated with PTFE, or other plastic materialwith low friction characteristics could alternatively be used for camsurface 15. A suitable adhesive, such as an epoxy, is used to secure thestainless steel rod to load beam 10. An alternate construction would beto weld or braze rod 12 to load beam 10.

The center line of load beam 10 (indicated in FIG. 1 by referencecharacter 18) passes through center of rotation 7 of rotation of rotaryactuator 7 and extends to the free end of load beam 10. In the presentembodiment, as will be appreciated by reference to FIG. 1, the centerline of lift tab 12 is not parallel to center line 18 of load beam 10.The angle of deviation between center line 18 of load beam 10 and thecenter line of lift tab 12 is indicated in FIG. 1 by the greek lettertheta (θ). In the embodiment illustrated herein, lift tab 12 extendsalong one edge of load beam 10, however other variations may be utilizedand it is not essential to the practice of the invention that lift tab12 have its central axis parallel with an edge of load beam 10. Theimportant relationship to be maintained with respect to the center lineof lift tab 12 and the center line of load beam 10 is that the angularrelationship of lift tab 12 provide an asymmetrical lifting force onload beam 10 to provide a roll attitude to slider 11 as it approachesthe surface of rigid disk 2 during loading of slider 11 above disk 2. Aswill be described more fully hereinafter, the roll applied to the slidermay be either "positive" or "negative" and both provide advantageousresults. After lift tab 12 has been moved out of contact with camsurface 15, load beam 10 (and slider 11) assume an attitude such thatthe lower surface of slider 11 and the lower surface of load beam 10 aresubstantially parallel to the plane of the surface of disk 2.

Referring to FIG. 3, head gimbal assembly 9 is illustrated inperspective and it will be appreciated that lift tab 12 extendsangularly with respect to the center line of load beam 10. Head gimbalassembly 9 may also be referred to as the "down" assembly since theread/write element (not shown) which is supported on slider body 11faces down toward the upper surface of rigid disk 2 as is illustrated inthe orientation in FIG. 1. With lift tab 12 in the orientation in FIG.3, the downward force of load beam 10 tilts the inner edge of the slider11 closer to the surface of disk 2 than the outer edge of slider 11torque valve thereby imparting a positive roll to slider 11.

Referring to FIG. 4, which is a view of the underside of head gimbalassembly 9 illustrated in FIG. 3, slider body 11 is supported on flexure19 for gimbaling movement above the surface of the disk 2. Head gimbalassembly 9 is of the Watrous-type, or also known as Whitney typesuspension; however, the particular type of suspension is not relevantwith respect to the present invention. Other suitable slider supportarrangements may be utilized to couple slider 11 to actuator body 6. Theasymmetrical relationship between the axis of lift tab 12 and the centerline of head gimbal assembly 9 may also be appreciated by reference toFIG. 2 which is a top plan view of head gimbal assembly 9.

Attention is directed to FIGS. 5a, 5b, 5c and 6-8 wherein therelationship between the lift tab and center line of the load beam towhich it is affixed, or of which it is a part, will be described toillustrate how a negative roll, no roll or a positive roll attitude isprovided to the slider affixed to the load beam. First, referring toFIG. 5a, load beam 25 is illustrated, and includes lift tab 26 having afree end 27. Supported near the end of load beam 25 is slider 28 whichis obscured by load beam 25, however edges 28a and 28b (also shown inFIGS. 6-8) are visible in this view. For convenience of explanation,load beam 25 is analogous to load beam 10 of the previous figures and isa "down" load beam. The center line of load beam 25 is indicated byreference character 29. With this configuration, the lift tab 26 extendsoutwardly and contacts a cam surface (not shown) along a center line 30.Line 31 indicates the point of contact between free end 27 of lift tab26 and center line 30 of cam surface. It will be appreciated byreference to FIG. 5a that the intersection between the cam center line(indicated by reference character 30) and the contact point, indicatedby line 31, of lift tab 26 is displaced from center line 29 of load beam25. The amount of deviation is indicated by the arrows pointing to thecenter line of load beam 25 and the line of contact between lift tab 26and the cam surface. As shown in FIG. 5a, this distance denoted as "-e"indicates the eccentricity of the geometry. The loading direction ofslider 28 onto a disk is indicated by the arrow denoted by referencecharacter 32. With the relationships indicated in FIG. 5a, a "negative"roll is imparted to slider 28 as is loaded onto a surface of a disk (notshown in FIG. 5a). Attention is directed to FIG. 6, which is a viewtaken along the lines 6--6 of FIG. 5a, which illustrates what is meantby a negative roll attitude which is imparted to slider 28 as it isbeing loaded above disk 33, the outer edge of which is indicated byreference character 34. As will be appreciated by reference to FIG. 6,edge 28a of slider 28 (which is nearer the center of disk 33 than isedge 28b) is higher above surface 35 than is edge 28b. By adjusting thepoint of contact between free end 27 of lift tab 26 and the contactpoint on the cam surface (not shown), the eccentricity value will bechanged and similarly the roll attitude of slider 28 will also bechanged. In the rigid disk drive of FIG. 1, this adjustment isachievable by use of cross-shaped slot 17 on cam assembly 14.

Referring to FIG. 5b, for illustrative purposes a no roll embodiment isillustrated. In FIG. 5b, load beam 25 is provided with lift tab 38having free end 39, and lift tab 38 is dimensioned such that free end 39contacts the cam surface (not shown) at intersection line center line 29of load beam 25. Since the cam surface contact corresponds to the centerline of load beam 25 no torque is applied to load beam 25 andaccordingly no roll results. Therefore, as will be appreciated byreference to FIG. 7, upon loading of slider 28 above surface 35 of disk33 edge 28a of slider 28 is approximately the same distance from surface35 as is edge 28b, accordingly this is a "no roll" or zero roll loadingattitude. As will be more fully pointed out hereinafter, it is desirablethat when loading a slider that either a positive or negative roll beapplied; however, the no roll or zero roll attitude is described forexplanatory purposes.

Referring to FIG. 5c, along with FIG. 8, a positive roll implementationof a load beam with lift tab is illustrated. In FIG. 5c, lift tab 40 isshorter in length than either of lift tabs 38 or 26. Therefore, whenfree end 41 of lift tab 40 intersects the cam (not shown) at cam centerline 31 the deviation between center line of load beam 25 and point ofcontact along cam center line 30 between the free end 41 of lift tab 40provides a torque which lifts edge 28b higher above surface 35 of disk33 than edge 28a as a result of the off center lifting provided byeccentricity "e". Referring to FIG. 8, it will be appreciated that edge28a of slider 28 is nearer the surface 35 of disk 33 than is edge 28b(which is near outer edge 34 of disk 33). As pointed out above, apositive roll attitude (as illustrated in FIG. 8), or a negative rollattitude (as illustrated in FIG. 6), are preferable to a no rollattitude as illustrated in FIG. 7. It will be appreciated that the lifttab utilized on the load beam could be positioned on the other side ofthe center line and by appropriately adjusting the length of the lifttab to achieve the contact point with the cam surface positive, negativeand no roll attitudes may be achieved.

The resulting torque is given by the following formula:

    Torque (T)=preload×eccentricity

where: preload=force exhibited by the load beam; and eccentricity=offsetdistance.

It has been found that the upper limit on torque is approximately 8-10gm-cm. The preferable values for a device according to applicants'invention is in the range of -0.5 gm-cm<T<+0.5 gm-cm. The "-" and "+" inthe foregoing range indicates negative and positive roll respectively.It will of course be appreciated that other torque values may beappropriate for different load beam structures.

Referring to FIG. 9, a highly enlarged portion of rigid disk drive 1 (intop plan view) adjacent to the end of head gimbal assembly 9 whichsupports slider 11 is illustrated. In FIG. 9, head gimbal assembly 9 isillustrated in three positions for purposes of illustrating how the headgimbal assembly 9 is initially loaded and placed into position forcooperation with cam assembly 14 and further how, as best illustrated inFIG. 10, head gimbal assembly 9 and a lower head gimbal assembly ifutilized, cooperates with cam assembly 14 for the dynamic loading andunloading of the sliders supported on the ends of respective head gimbalassemblies 9. The position of head gimbal assembly 9 to the left-mostportion of FIG. 9 is the beginning load position after installation ofthe rotary actuator into the drive for initial assembly purposes. Thisinitial installation position is illustrated in the left-hand portion ofFIG. 9 in which, it will be appreciated by reference to the figure, thatfree end 13 of lift tab 12 is unrestrained. Head gimbal assembly 9 isrotated in a counter-clockwise direction and free end 13 of lift tab 12travels over lobe portion 15a (as illustrated in FIG. 10) and with nofurther force being applied to rotate head gimbal assembly 9 free end 13comes to rest in the detent position in valley portion 15b of camsurface 15. In FIG. 9, this position is illustrated as the centralposition of the three positions of head gimbal assembly 9. This is theat rest (or unloaded) position for head gimbal assembly 9 and is wherethe assembly would be located prior to loading the heads on the disk. Inoperation, during start-up, power is applied the drive motor and rigiddisk 2 is brought up to rotational speed after which suitable current isapplied to the coil of the drive motor for the rotary actuator and headgimbal assembly 9 is rotated in a counter-clockwise direction duringwhich free end 13 moves to the right (as viewed in FIGS. 9 and 10),travels over lobe portion 15c and then down descending portion 15d ofcam surface 15 to the position illustrated in the right-----most portionof FIGS. 9 and 10 where slider 11 moves adjacent to the surface of disk2. As a result of the asymmetrical position of lift tab 12 on load beam9, during this loading operation the edge of slider 11 closer to theinner diameter of disk 2 will be lower than the edge of slider 11 nearerthe outer diameter of disk 2. This provides a positive roll attitude toslider 11. It will be recalled from above that a positive roll is thetype illustrated in FIG. 8.

Even though the dynamically loaded head does not contact the diskdirectly, after several thousand load/unloads a small amount of wearwhich appears as edge blending at one corner or edge of the head isevident. This blending is caused by the head contacting the higherasperities (4 to 8 microinches high) on the disk and burnishing themoff. Once the burnishing has occurred, both the lower asperity heightand blended head no longer contact each other and wear does notprogress. The head has sustained some minor wear (1 to 10 microinches)at a position of initial approach to the disk. This wear can be at asensitive area of the head or an insensitive area. The tunable rollfeature of the present invention permits controlling the location of theblending and guaranteeing that it occurs at a non-sensitive area.

The read/write element is generally located at the rear of the slider inorder to be as close as possible to the magnetic media (most often 5 to10 microinches flying height). If the blending occurs at the read/writegap, a change in gap separation may occur, changing the magneticperformance of the head. However, if the blending occurs along an edgeof the air bearing, the flying height of the whole head is littleaffected since its surface area is very large compared to the blendedarea. By introducing some roll into the head during loading andunloading, the blending is forced away from the sensitive area and thesystem integrity is improved.

Referring to FIG. 10, the slope of portion 15d of cam surface 15,measured with respect to the surface of rigid disk 2, may be in therange of from about 7° to 18°. The preferable range has been found to bebetween about 9° to 12°. As will be appreciated by reference to FIG. 10,rigid disk 2 extends at its outer periphery interiorly at the end 15e ofcam surface 15, as well as interiorly of the lower cam surface (notnumbered). Adjustability of cam assembly 14 in the direction generallyradial to rigid disk 2 permits, as will be appreciated by reference toFIGS. 9 and 10, adjustment of the landing position of slider body 11 onthe surface of rigid disk 2.

As mentioned previously, a second head gimbal assembly may be supportedbeneath head gimbal assembly 9. By utilizing a similar supportarrangement to that used for head gimbal assembly 9, the second headgimbal assembly with its associated slider and read/write element may bedynamically loaded into operative relationship with the lower surface ofdisk 2. In FIG. 10 reference characters 13a indicate the respectivedetent and load positions of the end of a lift tab used on a lowergimbal assembly. When upper and lower actuator arms are utilized, it isdesirable to include protective member 20 (illustrated in FIGS. 1, 9 and11) which extends intermediate the upper and lower head gimbalassemblies and is positioned in a plane generally parallel with theplane of disk 2. Referring to FIG. 11, a view along the lines of 11--11of FIG. 1 is provided to better illustrate protective member 20. In FIG.11, up load beam boa along with its associated up slider 11a and freeend 13a of up load beam 10a are illustrated, along with load beam 10,down slider 11 and lift tab 12 with its free end 13, all in the unloadedposition. For simplification of view, rigid disk 2 and the remainingportion of cam assembly 14 are not shown in FIG. 11. It will beappreciated by a reference to FIG. 11 that protective member 20 preventsthe unwanted impact between slider 11 and slider 11a should a shock betransmitted to disk drive 1 while the sliders are in the unloadedposition. When the head gimbal assemblies are positioned outside of thetravel above the surface of disk 2, by utilizing protective member 20shocks which may be transmitted to disk drive 1 which would move flexure19 and would otherwise cause slider 11 to impact up slider 11a of upload beam 10a are no longer a problem since protective member 20prevents slider-to-slider impacts. Without the use of protective member20, the read/write elements on their respective sliders may be damaged.Protective member 20 also limits destructive overtravel of flexure 19.Protective member 20 may either be a separate planar structure or formedas part of cam assembly 14. When formed as part of cam assembly 14 itwould of course be constructed of the same material; however, if aseparate member is utilized, it is preferred that it be composed of asoft resin impregnated with PTFE (which is also referred to by thetradename Teflon).

A second embodiment of the present invention is illustrated in FIGS.12a-12f. A better appreciation of the construction of the load beam inaccordance with the second embodiment of the present invention will beobtained by reference to FIGS. 12a-12j. Referring to FIG. 12a, load beam114-1 is shown in plan view with the underside, that is the side onwhich the read/write recording transducer will be mounted, facing upwardin this figure. Load beam 114-1 is referred to as the down load beam.Load beam 114-1 is unitary in construction and is preferably made fromType 302 non-magnetic stainless steel, having a thickness ofapproximately 0.0025 mm. As illustrated in FIG. 12a, load beam 114-1includes lift tab 117 which is semicircular in cross section at its freeend 180 as will be appreciated by reference to FIGS. 12c-1 and 12c-2.FIG. 12b illustrates load beam 114-1 in a side view taken along lines12b-12b of FIG. 12a. In the view of FIG. 12b, the load beam 114-1 isshown in a flat and unloaded orientation. Tabs, denominated 176, areutilized to secure the electrical wiring which extends to the free endof the load beam for connection to the read/write transducer head to bemounted at that location. The cross-section of load beam 114-1 takenalong lines 12e--12e is illustrated in FIG. 12e. The configuration ofload beam 114-1 changes from a generally flat orientation (with theexception of tabs 176 and stiffening channels 183 along the outer edgeof the load beam) as shown in FIG. 12f, the cross-section taken alonglines 12f--12f, to the configuration illustrated in FIG. 12e, and nearthe free end of load beam 114-1 the lift tab 117 is generallysemi-circular as is illustrated in FIG. 12c which shows the view of loadbeam 114-1 taken along the line 12c--12c in FIG. 12a. As will beappreciated by a reference to FIG. 12a, the center line of load beam114-1 is at the position indicated by the dashed line denominated 177.It will also be appreciated by reference to FIG. 12a that the curved endportion of lift tab 117 is not symmetrical with respect to center line177. This is also further illustrated in FIG. 12c where the center lineof load beam 114-1 is indicated by dashed line denominated 177. Thelowest point on lift tab 117 as measured from the center of radius 178'is indicated in FIG. 12c by reference line 178 which extends to thelower surface 179 of lift tab 117.

A better appreciation of the offset relationship between the free end oflift tab 117 and the centerline 177 of down load beam 114-1 will beobtained by reference to FIGS. 12c-1 and 12c-2. FIG. 12c-1 is a top planview of down load 114-1 showing the end portion thereof and a portion offlexure 184. For simplicity, cam assembly 118 and disk 2 are not shownin FIG. 12c-1. In FIG. 12c-2, which is a view taken along 12c-2 - 12c-2,it will be appreciated that the centerline 177 of load beam 114-1 is tothe left of the lowest point of tab lift 117 (indicated by 178) toprovide an offset distance 177/178. The free end of lift tab 117 isoffset toward the center of disk 2 to provide symmetrical lifting ofload beam 114-1 as it contacts cam surface 118-2. In FIG. 12c-2 lift tab117 is illustrated at the position where first contact is made with camsurface 118-2. The amount of the offset 177/178 is determined based onthe angular slope θ, which is measured between cam surface 118-2 andsurface 2' of disk 2, along with the radius of lift tab 117, the radiusbeing measured from center of radius 178' and the lower surface 179. Thelowest point of tab lift 117 is indicated at 178. The centerline offsetmay be calculated by the formula

    Centerline Offset=R sine θ

where

θ=angle between disk surface and cam surface

R=radius of curvature of load tab contacting the cam surface

With this offset, the lifting force on load beam 114-1 will be appliedsymmetrically along the centerline of load beam 114-1. In the preferredembodiment, the angle θ is 12°, and the radius of lift tab 117 at thepoint of contact with cam surface 118-2 is 0.46 mm. This results inoffset 177/178 being 0.095 mm. Similarly, the up load beams have theirtab ends offset, also toward the center of the disk, thereby ensuringthat the first surface of the load tab to contact its corresponding camsurface does so along the center line of the load beam. This centerlinecontact eliminates any twisting forces on the load beam.

Referring to FIG. 12d, a cross-sectional view taken along the line12d--12d of FIG. 12a, it will be appreciated that the free end 180 oflift tab 117 is offset downwardly (with respect to the surface of thedisk with which the load beam interfaces) from the plane of the flatsurface of load beam 114-1 indicated by reference character 181 in FIG.12d. This offset is provided to maximize the clearance between loadbeams when the read/write heads are unloaded. Referring to FIG. 12g,swage plate 182 is illustrated. Swage plate 182 is utilized inconnecting the load beam to the actuator body. Also illustrated in FIG.12g is flexure 184, only a portion of which is illustrated in thisfigure. Flexure 184 is utilized to support the read/write transducerhead in a flexible manner below the underside of its respective loadbeam. A perspective view of flexure 184 is illustrated in FIG. 12j.

A side view of load beam 114-1 with its swage plate 182 is illustratedin FIG. 12h which is a view taken along the lines 12h--12h in FIG. 12g.In FIG. 12h the load beam, flexure and associated read/write transducerare illustrated in loaded position. FIG. 12i illustrates load beam 114-1with associated read/write transducer and flexure in the unloadedposition. As illustrated in FIG. 12i, there is a normal downwardpositioning of the free end of load beam 114-1 which is by bending loadbeam 114-1 to provide a predetermined pre-tensioning.

In accordance with a third embodiment of the present invention, theactuator arm, which is also referred to as a load beam, is constructedusing a separate lift tab portion which is welded to a support armportion, rather than providing the actuator arm load beam as a unitarystructure, as in the case of the second embodiment described above inwhich load beam 114-1 is a unitary structure. Referring to FIG. 13, theactuator arm, referred to hereinafter is the load beam 50, isillustrated in a top plan view which shows the top side of load beam 50,which in the present invention is the down load beam. Load beam 50includes support arm portion 51 and lift tab portion 52. Lift tabportion 52 is laser welded to the support arm portion, the laser weldspots being indicated at 53. A portion of the flexure (which is alsolaser welded to support arm portion 51) is illustrated at 54. Thegeometry of lift tab portion 52 is preferably substantially the same asthe geometry of the lift tab portion of the unitary load beam 114-1illustrated in FIG. 12a. More particularly, the end portion 55 of lifttab portion 52 is axially offset toward the center of the disk withrespect to the centerline 56 of support arm portion 51. The relationshipbetween end portion 55 and support arm portion 51 is preferable the sameas that illustrated in FIGS. 12c-1 and 12c-2. End 57 of support armportion 51 is adapted for attachment to actuator body 6 of the rotaryactuator used in the drive. The offset relationship for end portion 55of lift tab portion 52 is preferable determined utilizing the sameformula relationships described above. With regard to the structuralcharacteristics of load beam 50, support arm portion 51 may beconstructed of the same material used and described above with respectto load beam 114-1. Lift tab portion 52 is preferable also constructedfrom the same material. Flexure 54, which is more fully illustrated inFIG. 14, is preferably constructed using the same material as flexure184 (illustrated in FIG. 12j).

Referring to FIG. 14, support arm portion 51 is illustrated in top planview to disclose its complete structure, which cannot be fully seen inFIG. 13 because of lift tab portion 52 being welded in place. Supportarm portion 51 includes tongue portion 61. As illustrated in FIG. 14,lift tab portion 52 includes alignment hole 62, support arm portion 51includes alignment hole 63 and flexure 54 includes alignment hole 64.

Flexure 54 is welded in place on the underside of support arm 51 andlift tab portion 52 is welded in place on the top side (the side shownin FIG. 14) and during the assembly process alignment holes 62, 63 and64 are utilized to position the parts in appropriate alignment. Whenwelded in place, dimple portion 65 of flexure 54 is positioned beneathtongue portion 61 of support arm 51 and provides a gimbaling support forthe slider body which is attached to the underside of the flexure 54.For ease of illustration, the slider body is not illustrated in thesefigures.

A fourth embodiment of the present invention is shown in FIG. 15 inwhich disk drive 151 is illustrated in a top plan view. Disk drive 151utilizes a rotary actuator which may be of a conventional type such asthat illustrated in embodiments 1-3 above. In FIG. 15, disk drive 151 isillustrated with the top cover removed for the convenience ofillustration of major components which are relevant to the presentinvention. Disk drive 151 includes magnetic media 152 of the disk typewhich includes a surface for receiving and storing informationmagnetically. Disks 152 and 152' are supported on spindle 153 which isdriven by a spin motor (not shown). Upper clamp 154 is used to retainmagnetic media 152 on spindle 153. Similarly, another clamp (not shown)is utilized to clamp magnetic media 152' to spindle 153. A clamp whichmay advantageously utilized in practice of the present invention may beone as described and claimed in U.S. patent application Ser. No.07/765,358 filed Sep. 25, 1991 by James A. Dunckley, which isincorporated herein by reference in its entirety. The spin motor issupported on baseplate 155 which may be made from any suitable rigidmaterial, such as, for example 6061-T6 aluminum alloy which ispreferably used. Alternatively, alloys of magnesium could be used.

Head gimbal assembly 156 (which will be described hereinafter in detail)supports air bearing slider 157 and upon rotation of the rotary actuatorallows air bearing slider 157 to access tracks on magnetic media 152.Head gimbal assembly 156 is supported on actuator body 158, which issupported for rotation about a center of rotation 159. An actuator coil(not shown) is positioned beneath return plate 160 which forms a portionof the actuator drive motor for the rotary actuator. Rotary actuatorssuitable for use in driving head gimbal assembly 156 are well known tothose skilled in the art and accordingly further description would onlyserve to unnecessarily lengthen this specification.

Dynamic loading and unloading of air bearing slider 157 is facilitatedthrough the use of cam assembly 161 which is mounted and positioned onbaseplate 155 by, among other things, a threaded bolt 162. As describedin detail below, cam assembly 161 is positioned on baseplate 155 byprojections 178 and 179, illustrated in FIGS. 19-21 and 23, which matewith apertures in baseplate 155. As pointed out below, cam assembly 161may be immovably secured to baseplate 155 prior to installing the disks.Accordingly, cam assembly 161 may be secured to baseplate 155 by asuitable adhesive instead of by bolt 162. Additionally, the cam assemblycould be formed integrally with the baseplate. Lift tab 163 extendsbeyond the end of load beam 164, and lift tab 163 contacts and movesalong the portion of cam surface indicated at 165 of the cam portion 166of cam assembly 161. Cam assembly 161 is illustrated in extensive detailbelow.

Also illustrated in FIG. 15 is cable 167 which is connected at one endto the transducer element in air bearing slider 157 and at the other endis connected to flexible conductor 168. Flexible conductor 168 isutilized since it provides minimum restriction in the movement of headgimbal assembly 156, and therefore provides a convenient way ofconducting signals from the transducer element of air bearing slider 157to read/write preamp integrated circuit 169.

As will be appreciated by reference to FIG. 15, air bearing slider 157is in a position such that it is unloaded from the surface 188 ofmagnetic media 152. Also illustrated in FIG. 15, head gimbal assembly156 is in an unloaded, rest position. As will also be appreciated byreference to FIG. 15, no portion of cam assembly 161 extends over eithersurface 188 or surface 193 (FIG. 23) of magnetic media 152. It will benoted that the right-most portion of cam assembly 161 is separated fromouter edge 170 of magnetic media 152 by a gap. As will further beappreciated by reference to the figures which follow and theaccompanying discussion, cam portion 166 includes a contour whichpermits rotation of head gimbal assembly 156 in the direction oppositethat which used for loading air bearing slider 157 onto media 152, theadditional movement permitting head gimbal assembly 156 to be movedsufficiently to allow installation of magnetic media 152 and 152' (FIG.23) without interfering with the head gimbal assembly for any of themedia. Although a portion of head gimbal assembly 156 does extend overthe surface of media 152 when the head gimbal assembly is in the restposition, sufficient room is provided in disk drive 151 to allowrotation of the head gimbal assembly in a clockwise direction (as viewedin FIG. 15) to so that disks 152 and 152' may be installed after headgimbal assembly 156 has been secured in drive 151. Additionally, sinceno portion of cam assembly 161 extends within the area occupied bymagnetic media 152 or 152', both head gimbal assembly 156 (and the headgimbal assemblies used for the other surfaces of the media) and camassembly 161 may be installed in disk drive 151 prior to theinstallation of the magnetic disks. The two foregoing characteristics ofthe cam assembly 161 permits efficient assembly of disk drive 151, whichmay be accomplished for example by installing cam assembly 161 onbaseplate 155; installing the actuator drive motor and head gimbalassembly; positioning head gimbal assembly to the left (as illustratedin FIG. 15) such that no part of head gimbal assemblies will be withinthe installation space of magnetic media 152 and 152'. In theillustrated, compact version of drive 151, this involves rotating thehead gimbal assemblies to a position such that lift tabs 163 and 189(FIG. 21) are to the left (as viewed in FIG. 15 and 16) of cam portion166 and no longer are in contact with the cam surface. Therefore, afterthe disks have been installed the lift tabs must be re-loaded onto theirrespective cam surface. In view of this, trailing portion 185 includesrounded portions 203 and 204 (FIG. 21) to facilitate moving lift tabs163 and 189 back into position on cam portion 176 after the media hasbeen installed. Next, magnetic media 152 and 152' are positioned onspindle 153 and clamped into place. Using this process, it is no longernecessary to either move the cam assembly out of the way of a disk beinginstalled or to carefully position a disk with respect to an alreadyinstalled cam assembly in which a part of the cam assembly extends overa surface of the disks. After magnetic media 152 and 152' have beenclamped into place, the head gimbal assembly 156 and the other headgimbal assemblies below head gimbal assembly 156 (and thus not visiblein FIG. 15) are then rotated into the rest position as illustrated inFIG. 15.

Referring to FIG. 16, disk drive 151 is illustrated in a view in whichhead gimbal assembly 156 has been rotated toward the center of magneticmedia 152 and air bearing slider 157 has been moved into a loadedposition above surface 188 of disk 152. At this position, lift tab 163has been moved to near the right-most edge of cam surface 165, and aswill be appreciated from the description which follows, is on downwardslanted portion 187 (FIG. 21) of a cam surface 165.

In the views of both FIGS. 15 and 16, head gimbal assembly 156denominated is a "down" head gimbal assembly since the read/writetransducer (not shown) of air bearing slider 157 is facing downward withrespect to surface 188 of magnetic media 152. Although not illustratedin FIGS. 15 or 16, "up" head gimbal assemblies are utilized to providethe recording and playback of information on lower surface 193 ofmagnetic media 152 and lower surface 2012 of magnetic media 152'. Downhead gimbal assembly 156 is illustrated in greater detail in FIG. 17.

FIG. 17 illustrates in an enlarged view head gimbal assembly 156 asshown from the top as illustrated in FIG. 15. Insulating cover 176 forcable 167 is illustrated in FIGS. 17 and 17A. As mentioned above, headgimbal assembly 156 is a down head gimbal assembly since the transducerof air bearing slider 157 is facing downward as viewed from the top ofthe disk drive 151. Load beam 164 is preferably of the low-profile type,and may be, for example, a type 16 available from Hutchinson TechnologyIncorporated, located in Hutchinson, Minn. In the preferred embodiment,lift tab 163 is provided by welding or gluing to the upper surface ofload beam 164 lift rod 171, which may be for example non-magneticstainless steel. A suitable adhesive for affixing lift rod 171 to loadbeam 164 is Ablestick 868-7. To reduce friction between lift tab 163 andthe cam surface 165, the surface finish of lift rod 171 should by on theorder of 8 micro inch finish. Lift rod 171 may be made from gauge 304Wstainless steel hypodermic needle stock. It is, however, not essentialthat a rod be utilized to provide lift tab 163. Alternatively, load beam164 could be modified to include an extension of the load beam materialto the same area covered by a portion of rod 171 which extends beyondthe parameter of load beam 164 as illustrated in FIG. 17 and provide alift tab. With this alternative, the extension of the load beam materialwould preferably be formed into a cam follower, such as a semicircularportion, where the lift tab portion 163 contacts cam surface 165.

The centerline of load beam 164 is indicated by dashed line 172. Thecenterline of lift tab portion 163 is indicated by reference character172, and as will be appreciated by reference to FIG. 17, there isangular displacement α1 between centerlines 172 and 173. When utilizingthe Hutchinson Technology load beam it is convenient to attach rod 171along the edge adjacent to the upturned flange 174 of load beam 164.This provides angle α1 as being approximately 6.6 degrees. This angle isnot critical and the portion of lift tab 163 which contacts cam surface165 could be parallel to centerline 172 of load beam 164. Angle α1 couldbe in the range of from 0 degrees to about 45 degrees.

Air bearing slider 157 may be of any suitable, generally available type,and it is up to the disk drive designer to select an air bearing slidersuitable for the particular characteristics of the media being utilized.Suitable air bearing sliders may be purchased from companies such asSAE/KAIFA of Hong Kong, Read-Rite of Milpitas, Calif., or AppliedMagnetic Corporation of Goleta, Calif. Air bearing slider 157 isattached to the gimbal portion of head gimbal assembly 156 by astructural epoxy resin, such as, for example, Ablestick 868-7.

Load beam 164 may be attached to actuator body 158 utilizing thetechniques such as those disclosed earlier herein, for example by usinga swage plate as illustrated and described in connection with FIGS. 12hand 12i.

Head gimbal assembly 156 includes a modification to the Hutchinson type16 load beam. More particularly the portion of load beam 164 aboutcenterline 172 for the Hutchinson type 16 are typically symmetrical,however to accommodate and provide additional room for the installationof disk, a portion of the Hutchinson load beam beginning at point 175and extending toward centerline 172 has been cut away toward the end ofload beam 164. Also, unnecessary wire tabs are removed from the side ofload beam 164 which includes lift rod 171.

FIG. 17A illustrates a side view, taken along lines 17A--17A of FIG. 17,of head gimbal assembly 156. The "up" load beams (not shown since theyare directly beneath the down load beam 156) are constructed in the samemanner as head gimbal assembly 156, however of course the lift rod 171is placed along the outer edge of the load beam and the slider is facingupward as viewed in FIG. 15 and the wires connected to the associatedslider are re-routed.

A better appreciation of cam assembly 161 will be gained by reference toFIGS. 18-22. FIG. 18 is an enlarged view of cam assembly 161 taken fromthe top as viewed in FIG. 15. Cam assembly 161 is preferably molded froma low friction material such as, for example, DuPont Delrin II 900F BK602. As will be appreciated by reference to the explanation below, camassembly 161 is produced as a modular unit which permits the utilizationof several cam assemblies to provide cam surfaces for disk driveutilizing a plurality of disks. The utilization of two cam assemblies161 in a stacked arrangement for magnetic media 152 and 152' isillustrated in FIG. 23.

Cam assembly 161, although preferably molded as a unitary element, maybe thought of functionally as having a cam portion 166 which extendsfrom body portion 177. Body portion 177 includes projections 178 and 179which extend from the lower portion of body 177 and fit into openings inbaseplate 155 to correctly position cam assembly 161 with respect tohead gimbal assembly 164 and magnetic disk 152. Returning to FIG. 17,opening 180 is provided in body portion 177 to permit installation ofthreaded bolt 162 to secure the cam assembly to baseplate 155.Additionally, apertures 181 and 182 extend from the top surface 184 ofcam assembly 161 downward for a predetermined distance (as illustratedin FIG. 19). These apertures are sized such that they can receiveprojections 178 and 179 from a second cam assembly to providestackability as indicated above.

Referring to FIG. 19, recessed area 183 is provided to permit the headof bolt 162 (FIG. 15) to be below top surface 184 of body portion 177.Also illustrated in FIG. 19 is the configuration of the trailing portion185 of cam portion 166.

FIG. 20 is a view of cam assembly 161 taken along the lines 20--20 ofFIG. 18. In FIG. 20 the leading portion 186 of cam portion 166 isillustrated, as is cam surface 165 along which lift tab 163 travels.Also in FIG. 20 it will be noted that projection 179 is oblong. Thisoblong shape is also illustrated in FIG. 22 which is a bottom view ofcam assembly 161 taken along the lines 22--22 of FIG. 21. Although bodyportion 177 is illustrated as being rectangularly shaped, other shapesmay be utilized. Body portion 177 serves to secure cam portion 166 tobaseplate 155 and position cam portion at a location which is anappropriate height with respect to the surfaces of the associated media.In FIG. 20, it will be appreciated that the upper and lower surfaces ofcam portion 166 extend toward the center of body 177 to provide aminimum contact surface for the lift tab, thereby reducing frictionalforces. To reduce friction between the lift tabs 163 and 189 and theirassociated cam surfaces, relief surfaces 207 and 208, respectively, areformed on cam portion 166. The angle of relief surface 207 with respectto the surface 188 of media 152 should be greater than the angle of lifttab 163 with respect to surface 188. The same relationship holds truewith respect to relief surface 208 and lift tab 189, both with respectto surface 193.

FIG. 21 is a view taken along lines 21--21 in FIG. 15 where forconvenience only the upper magnetic media 152 and the upper cam assembly161 are shown. Disk drive 151 is a two media version, however since thedisk 152' and the head gimbal assemblies for the other surfaces extenddirectly below those shown in FIG. 15, they are not illustrated in theview of either FIG. 15 or 16. Turning to FIG. 21, lift tab 163 isillustrated in the position along loading surface portion 187 of camsurface 165 at which slider 157 is beginning to fly over the surface 188of magnetic media 152. A second load tab 189 for the up head gimbalassembly is also illustrated. The angular relationship between loadingsurface portion 187 and the surface 188 of media 152 is indicated by θ2.Line portion 190 indicates the angular position of loading surfaceportion 187 and line portion 191 is parallel to surface 188 of media152. Angle θ2 approximately 12 degrees in the preferred embodiment,however a typical acceptable range is from about 5 degrees to about 15degrees. Similarly, the angular relationship between loading surfaceportion 192 on the lower side of cam portion 166 and lower surface 193of media 152 would be in the same range. It will be noted from FIG. 21that extending to the right as viewed in FIG. 21 that a flat portion 194of cam surface 165 is provided, this flat portion 194 in this embodimentbeing generally parallel to surface 188 of disk 152. This flat portionensures that air bearing slider 157 is completely removed from contactarea portion of surface 188 before the head gimbal assembly is moved tothe rest position as illustrated in FIG. 15. When the head gimbalassemblies are moved to the rest position, the respective lift tabs willbe positioned at location 195 and 196 for the upper and lower headgimbal assemblies respectively. The angular relationship between thedescending surface portion 197 with respect to surface 188 is preferablyabout 15 degrees, however an acceptable range for this angle is fromabout 5 to 25 degrees. The angular relationship between ascendingportion 198 of the trailing portion 185 with respect to surface 188 ispreferably 15 degrees, however this angle could range from about 5 toabout 25 degrees. As described above, rounded portions 203 and 204permit easy re-positioning of lift tabs 163 and 189 onto theirassociated portions of the cam surface. Line portion 205 indicates atangential line with respect to rounded surface 204, and line portion206 is parallel to surface 193 of disk 152. Angle α2, which provides anindication of the slope of rounded portion 204 with respect to surface193, should be selected to be in the range of from about 0 degrees toabout 60 degrees. The same angular relationship with respect to roundedportion 203 and surface 188 applies. The angular relationships with thecorresponding portions along the lower surface of cam portion 166 wouldbe the same with respect to lower surface 193 of media 152.

The underside of cam assembly 161 is viewed along lines 22--22 isillustrated in FIG. 22. It will be noted that the beginning of loadposition for lower load tab 189 is illustrated near the leading edge 186of cam portion 166. Additionally, rest location 196 for the lower headgimbal assembly as illustrated. Referring to FIG. 23, a stackedarrangement of cam assemblies 161 and 161' is illustrated. This view isa complete sectional view taken along the lines 21--21 of FIG. 16 toillustrate disk 152' and second cam assembly unit 161 which are utilizedin the disk drive 151 having a pair of disks. For convenience ofreference, the reference characters for lower cam assembly 161' utilizecorresponding numbers to those for cam assembly 161. Referring to FIG.23, it will be noted that projections 178 and 179 interfit with openings182 and 181 respectively to interlock upper cam assembly 161 with lowercam assembly 161. Lower projections 178 and 179 interfit withcorresponding openings in baseplate 155 to position both the upper andlower cam assemblies at the appropriate location with regard to the headgimbal assemblies and disks 152 and 152'.

Those skilled in the art will of course appreciate that the variousmodifications may be made to our invention without departing from thespirit and scope thereof and that the foregoing description isillustrative of several embodiments of our invention, however the scopeof our invention is governed by the appended claims.

We claim:
 1. A disk drive comprising:a baseplate; a first disk forrecording and playback of information, said disk supported on saidbaseplate for rotation, and said disk having inner and outer edgesdefining a disk area; a first elongated actuator arm including a loadbeam, said actuator arm being pivotally supported about a center ofrotation on said baseplate for rotation of one end of said load beam inplane substantially parallel to a surface of said disk, said load beamincluding at its outermost end a lift tab extending from said one end ofsaid load beam, said lift tab being positioned such that a centerline ofsaid lift tab is angularly displaced with respect to the longitudinalaxis of said actuator arm; a slider body including a read/writetransducer element; means connecting said slider body to said load beamat a position intermediate said center of rotation and said lift tab;and a cam assembly supported on said baseplate adjacent to said lift taband the outer edge of said disk, said cam assembly including a first camsurface positioned in operative relationship with said lift tab, andsaid cam assembly being positioned on said baseplate at a position suchthat no portion of said cam assembly extends within said disk area, saidlift tab contacting said first cam surface and in cooperation with saidfirst cam surface providing a lifting force to said load beam.
 2. A diskdrive according to claim 1, wherein said cam assembly furthercomprises:a second cam surface and wherein said disk drive includes asecond elongated actuator arm including an associated load beam, saidsecond elongated actuator arm being pivotally supported about a centerof rotation on said baseplate for rotation of one end of said associatedload beam in a plane substantially parallel to the opposite surface ofsaid disk, said associated load beam including at its outermost end anassociated lift tab extending from said one end of said associated loadbeam, said associated lift tab being positioned such that a centerlineof said associated lift tab is angularly displaced with respect to thelongitudinal axis of said second elongated actuator arm; a second sliderbody including a read/write transducer element; means connecting saidsecond slider body to said associated load beam at a positionintermediate said center of rotation and said associated lift tab, saidassociated lift tab contacting said second cam surface and incooperation with said second cam surface providing a lifting force tosaid associated load beam.
 3. A disk drive according to claim 2, whereinthe angular displacement between the centerline of each lift tab and thelongitudinal axis of its respective actuator arm is greater than zerodegrees but equal to or less than 45 degrees.
 4. A disk drive accordingto claim 1, wherein an angle between the centerline of said lift tab andthe longitudinal axis of said actuator arm is greater than zero degreesbut equal to or less than 45 degrees.
 5. A disk drive according to claim1, wherein said cam assembly includes a projection adapted to fit andfurther wherein said baseplate includes an aperture adapted to receivesaid projection, whereby said cam assembly is located with respect tosaid disk.
 6. A disk drive according to claim 1, wherein said camassembly comprises a body portion and a cam portion, wherein said bodyportion includes a projection extending from one surface of said bodyportion, and wherein said body portion includes an aperture in anothersurface of said body portion.
 7. A disk drive according to claim 1,wherein said cam surface includes a contour which permits rotationalmovement of said actuator arm in a direction opposite to the directionof rotation of said actuator arm during positioning of said slider bodyover the surface of said first disk and in an amount sufficient topermit installation of said disk without interference with said actuatorarm.
 8. A disk drive according to claim 1, wherein said lift tab iscylindrical.
 9. A disk drive comprising:a baseplate; a first disk forrecording and playback of information, said disk supported on saidbaseplate for rotation, and said disk having inner and outer edgesdefining a disk area; a first elongated actuator arm including a loadbeam, said actuator arm being pivotally supported about a center ofrotation on said baseplate for rotation of one end of said load beam inplane substantially parallel to a surface of said disk, said load beamincluding at its outermost end a lift tab extending from said one end ofsaid load beam, said lift tab including a cam contact portion having acenterline which is offset with respect to the longitudinal axis of saidactuator arm, wherein the offset is in a direction parallel to thesurface of the disk; a slider body including a read/write transducerelement; means connecting said slider body to said load beam at aposition intermediate said center of rotation and said lift tab; and acam assembly supported on said baseplate adjacent to said lift tab andthe outer edge of said disk, said cam assembly including a first camsurface positioned in operative relationship with said lift tab, andsaid cam assembly being positioned on said baseplate at a position suchthat no portion of said cam assembly extends within said disk area, saidlift tab contact portion contacting said first cam surface and incooperation with said first cam surface providing a lifting force tosaid load beam.
 10. A disk drive according to claim 9, wherein said camassembly further comprises:a second cam surface and wherein said diskdrive includes a second elongated actuator arm including an associatedload beam, said second elongated actuator arm being pivotally supportedabout a center of rotation on said baseplate for rotation of one end ofsaid associated load beam in a plane substantially parallel to theopposite surface of said disk, said associated load beam including atits outermost end an associated lift tab extending from said one end ofsaid associated load beam, said associated lift tab including a camcontact portion having a centerline which is offset with respect to thelongitudinal axis of said second elongated actuator arm, wherein theoffset is in a direction parallel to the opposite surface of the disk; asecond slider body including a read/write transducer element; meansconnecting said second slider body to said associated load beam at aposition intermediate said center of rotation and said associated lifttab, said cam contact portion of said associated lift tab contactingsaid second cam surface and in cooperation with said second cam surfaceproviding a lifting force to said associated load beam.
 11. A disk driveaccording to claim 9, wherein said cam assembly includes a projectionadapted to fit and further wherein said baseplate includes an apertureadapted to receive said projection, whereby said cam assembly is locatedwith respect to said disk.
 12. A disk drive according to claim 9,wherein said cam assembly comprises a body portion and a cam portion,wherein said body portion includes a projection extending from onesurface of said body portion, and wherein said body portion includes anaperture in another surface of said body portion.
 13. A disk driveaccording to claim 9, wherein said cam surface includes a contour whichpermits rotational movement of said actuator arm in a direction oppositeto the direction of rotation of said actuator arm during positioning ofsaid slider body over the surface of said first disk and in an amountsufficient to permit installation of said disk without interference withsaid actuator arm.